1 Topic by doppler

  • doppler
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Topic: Extruder to Bed Gap Distance

I'm a new Solidoodle 3 owner, and for the most part once I abandoned hope that the kapton tape was ever really going to hold my prints, have been fairly successful at 3d prints.  However...

I've read around, a lot, and there doesn't seem to be a scientific number of what to set the gap between the extruder and the bed.  I've been playing it by feel, and for the most part have good prints, but having one of two problem depending on what side of gap I've gone.

I'm using a feeler gauge to measure the gap;

At 0.15mm gap, the print is stuck well to the glass (hair sprayed) and has good solid consistency, but the extruder touches the layer below when printing, which when you print the last layer is a bit visually annoying as it draws lines through the top layer if the head backtracks through the print... I've also had times when it starts ruining the print because the x/y details are so small the extruder just smashes them up.

At 0.35mm gap, the print isn't well stuck to the glass, and has less of a solid consistency, being more stringy.  The extruder however never interfere's with the layer below.

I've played with different gaps inbetween, anything below 0.35mm seems to suffer the extruder touching....  Oh I should note I'm printing at 0.3mm with a 0.3mm start layer.

Is this what should be expected with the extruder touching the layer below?

Thanks
  Andrew

2 Reply by Claghorn

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Re: Extruder to Bed Gap Distance

I found that trying to measure it was hopeless (for me, anyway). I've taken to printing the calibration cube with just 1 layer on the bottom, then seeing what that layer looks like. If the filaments leave gaps between them, I crank the z-stop screw so the extruder will be closer to the bed till I get one to print what looks like a solid well formed single layer on the bottom of the cube.

Claghorn's Website

3 Reply by satman49

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Re: Extruder to Bed Gap Distance

In this day and age of high tech, You would think SD would have tech specs for that.LOL they used a Metro card, what ever that is to check bed level.

SD3, E3D hotend,linear bearing on x/y axis',pillow block bearing on y conneting rod, ball bearngs on front y axis, fan on y stepper motor.

4 Reply by doppler

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Re: Extruder to Bed Gap Distance

Thank you both for your replies which were echo's of what i've found in my searches, and this isn't a specific issue to SD, but to the industry in general.

However I did stumble upon a thread here on the similar vein and it pointed me to a bunch of calibrations I hadn't done, didn't think I needed to do on a new printer, but it is a partial DIY unit, so I have now since this post;

1) Calibrated the Extruder Stepper using the 100mm Youtube video example, my SD was moving 127mm originally
2) Printed a calibration cube, with no infill and 0.42 thickness and stop before it hits the top.  I was printing at 0.39 on the first one, adjusted the multiplier to bring it to 0.42, next one hit bang on.   

So there is much less dragging through material, as well now there is less material being extruded, I'm pretty happy with the prints now.

I did also try one more adjustment in Slic3r, there is under printer a setting to drop the Z Xmm on retract, given that the dragging was happening during a retract it struck me as a useful setting.  I tried it it at 0.6mm, yes no dragging, printing time increased.  The print looks really good except the first layer didn't completely stick to the layer above, there is a thread of the perimeter hanging loose...  and my first print curled up and didn't stick well with this setting, but I've been printing a lot of these "sharks" so I rehair sprayed the glass and the 2nd one printed with the same settings still had the one loose perimeter filament on the first layer, but didn't curl and stuck fine....

5 Reply by IanJohnson

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Re: Extruder to Bed Gap Distance

Z lift can be problematic due to backlash in the Z axis.  It might not return to the same place it was before the retract.  There are several solutions around, do a search for Z backlash.  In the meantime, it's better to leave it off.  The best time to use it is when you print something tall and thin that tends to get knocked over or broken by the nozzle.

6 Reply by pirvan

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Re: Extruder to Bed Gap Distance

I used a feeler gauge, .15mm or something like it, also a standard business card is about the right thickness. 

The head to surface gap is only important as it relates to getting good solid adhesion to the print surface, and it only affects your first layer. But it's also your print's foundation.  If it doesn't stick well your print will suffer.

What I do, is tell Slic3r to print 3 or 4 skirt/brim loops and watch it as it starts to print.  You'll want a nice, flat, partially squished layer.  If the filament doesn't look like that, it's thin and not sticking to the glass, kill the print and adjust your "Z" stop screw counterclockwise a 1/4 turn.  Re-home your "Z", and hit print again.  Eventually you'll hit on just the right setting, and it might not be even close to what you originally got with the feeler gauge.

Personally I don't think that actual thickness of the first layer is all that critical (unless you're going for perfect dimensions). Once that first layer is put down, all subsequent layers are relative to the layer thickness value you chose, and your printer's ability to repeat that accurately (see Ian's comment on backlash).

NOTE:  Something else I found is that if you're using glass for your print surface, the head to glass gap will change (shrink) as the glass gets hotter, because it expands ever so slightly.  So if you adjusted the gap with the heaters OFF, you'll find the gap is smaller once the print bed has up to temperature.

I'm not sure if anyone else has experienced this, but I have.

To print or, 3D print, that is the question...
SD3 printer w/too many mods,  Printrbot Simple Maker Ed.,  FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.